1. Industrial Application Fields
This invention relates to silicone oil for low temperature use in mechanical applications, particularly to silicone oil for low temperature use having a superior fluidity under low temperature conditions and a small dependence of viscosity upon temperature.
2. Conventional Techniques
Conventionally, dimethyl silicone oil has been widely utilized as a mechanical use silicone oil. This dimethyl silicone oil possesses a low temperature coefficient of viscosity, 0.6; therefore, its viscosity increase at low temperature is small compared to other types of mechanical oil, such as general purpose types of mineral oil and synthetic oil. However, its fluidity point is -50.degree. C.; thus, a disadvantage of the dimethyl silicone oil is inability to maintain an oily character at the low temperatures of typical usage.
On the other hand, a known silicone oil which possesses a high fluidity at a temperature of at most -50.degree. C. is methyl phenyl silicone oil which contains a certain amount of substituted phenyl groups in the molecule. This methyl phenyl silicone oil has a fluidity point -65.degree. to -70.degree. C., lower than that of the dimethyl silicone oil; however, its temperature coefficient of viscosity is 0.65, which is higher than that of the dimethyl silicone oil. Therefore, the methyl phenyl silicone oil tends to be higher in viscosity at low temperature and becomes harder to use.
As a result, development for mechanical use of an oil with a lower temperature coefficient of viscosity than the dimethyl silicone oil and with a lower fluidity point than the methyl phenyl silicone oil has been strongly desired.